Incinerator for the combustion of waste products, particularly plastic materials

ABSTRACT

In an incinerator comprising two combustion chambers, the primary combustion chamber comprising refractory ceramic elements located adjacent to one another so as to form inclined continuous guide surfaces and means for supplying primary combustion air to said primary combustion chamber opening into said chamber at different levels above the bottom thereof.

United States Patent Faurholdt [451 June 20, 1972 s41 INCINERATOR FORTHE 1 3,495,555 2/1970 Boyd et al ..1 10/8 3,190,244 6/1965 HOSkl son.....110/1s COMBUSTION 0F WASTE PRODUCTS 2,961,977 11/1960 colerr i an..1 10/8 PARTICULARLY PLASTIC MATERIALS Primary Examiner-Kenneth W.Sprague 72 l t Be t F holdt T 134, 2730 .1 ne'l' levy gznm omemseve]Attorney-Watson, Cole, Grmdle & Watson [22] Filed: April 24, 1970 21Appl. No.: 31,507 [571 ABSTMCT In an incinerator comprising twocombustion chambers, the primary combustion chamber comprisingrefractory ceramic [52] U.S.Cl ..110/8 A, 110/8 C, ll0/l8C elementslocated adjacent to one another so as to form [51] Int. CLm... "F2385/12 inclined continuous guide Surfaces and means for supplying [58]Field of Search ..1 10/7, 8, 8 A, 8 C, 18, 18 C primary combustion airto i primary combustion Chamber opening into said chamber at differentlevels above the bottom [56] References Cited thereof. 1

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INVENTOR 77412 G za BY af dzzw (5P4 yfi'mm/ Y a ATTORNEYS PATENTEDmzoI972 SHEET t 0F 7 INVENTOR ATTORNEYS SHEET 60F 7 6 14; K -15 o o o o o oo l8 v INVENTOR ATTORNEY-S s/ I 5 BY f (M r PATENT Emma [s12 INCINERATORFOR THE COMBUSTION OF WASTE PRODUCTS, PARTICULARLY PLASTIC MATERIALSBACKGROUND OF THE INVENTION This invention relates to an incinerator forthe combustion of waste products and particularly plastic materialscomprising a primary combustion chamber, means for supplying primarycombustion air to said primary combustion chamber and a secondarycombustion chamber which is thermally isolated from the primarycombustion chamber and has means for initiating a secondary combustion.

The still increasing use of articles made from plastic materials andparticularly disposable plastic materials presents problems with respectto the disposal of such articles. In order to reduce the risk ofinfection and to eliminate the cleaning of used articles it isimportant, particularly in hospitals and laboratories in whichdisposable plastic materials find widespread use that these plasticarticles can be quickly and easily destructed by incineration.

Also in industries in which plastic materials are produced or utilized,serious problems are encountered when waste products made from plasticmaterials have to be destroyed because said plastic materials cannot bedecomposed as ordinary refuse when stored in refuse dumps, compostheaps, etc.

In the prior art incinerators the destruction of plastic materialspresents serious problems because these plastic materials burn in amanner which is very different from that of household refuse.

The problems which are encountered during the incineration of plasticmaterials in prior art incinerators comprising a grate supporting theplastic materials are due to the fact that the grate quickly stopsfunctioning in the normal manner because the holes in said grate throughwhich the air is supplied beeome clogged. This clogging has the effectof initiating a destruction of the grate if it is made from commonlyused materials, such as cast steel alloys.

Other problems are due to the high soot content in the flue gasesleaving incinerators in which plastic materials are incinerated. Thissoot content which is due to an incomplete combustion stronglycontaminates the atmosphere and is a nuisance in the area surroundingsuch incinerators.

The reason forthese difficulties is that plastic materials possess theproperty of becoming soft and melting before they are ignited and burn.If refuse containing plastic materials is introduced into and ignited inan incinerator in which the grate consists of perforated grate elementsof cast iron or grate lamellae separated by passages for supplying air,the openings or passages in the grate become clogged whether it isconstructed as a step grate, a plane grate, or as an inclined gratebecause of the melting of said plastic materials. During the combustionwhich takes place on the basis of the combustion air which is suppliedto the refuse without passing through the grate, very high temperaturesare developed on the upper surface of the grate. Because of the cloggingof the passages in the grate the latter is not subjected to the coolingwhich nor mally takes place during the passage of the cool combustionair through the grate passages. Thus, the grate, e.g., made from castiron is heated to very. high temperatures and said heating causes anirreversible increase of volume.

Furthermore, the plastic materials possess the property that even whenheated to a moderate temperature large amounts of gases are developedand the amount of said gases increases exponentially with increasingheating temperatures. Thus, if refuse containingplastic materials isintroduced into and ignited in the above mentioned incinerators, largeamounts of gases containing carbon particles are quickly formed in thezone above the refuse layer and said carbon particles escape from thecombustion chamber together with the flue gases. If it is attempted toavoid the formation of these carbon particles by introducing morecombustion air in the combustion chamber, the increased amount of heatresulting from the secondary combustion causes a generation of stillgreater amounts of gases and sooty carbon particles. Thus, the

problems are progressively increased until the gases and carbonparticles have been completely burned away. At this time the supply of alarge amount of secondary air effects a strong cooling of the combustionchamber, thus decreasing the combustion temperature of the materialwhich has not been completely burned out. This temperature decrease alsoleads to the fonnation of soot which leaves the incinerator togetherwith the flue gases.

As mentioned above the rate at which the generation of volatile gasesand soot particles takes place within the primary combustion chamberdepends on the generation of heat and consequently the temperaturewithin the primary combustion chamber. However, by effecting thecombustion in two thermally separated chambers it can be prevented thatthe generation of heat and the increase of temperature resulting fromthe secondary combustion influence the combustion process in the primarycombustion chamber and the generation of gases and sooty particleswithin said chamber.

The object of the present invention is to provide an incinerator whichis suitable for the combustion of articles made from plastic materialsand other organic materials having similar combustion properties andwhich eliminates the drawbacks of the prior art incinerators.

SUMMARY .OF THE INVENTION According to the invention there is providedan incinerator having a primary combustion chamber which comprisesinclined continuous guide. surfaces consisting of guide elements madefrom a refractory ceramic material and in which the means for supplyingprimary combustion air to said primary combustion chamber open into saidchamber at different levels above the bottom thereof.

I When incinerating plastic materials in the incinerator according tothe invention, the plastic material while melting flows down along theinclined guide surfaces and during said movement the temperature isincreased to a value such that a gasification takes place. Due to thefact that the primary com bustion air is supplied at different levelsabove the bottom of the chamber, there is effected an intimate mixing ofthe primary combustion air and the compounds formed during saidgasification which compounds subsequently burn.

In a preferred embodiment of the incinerator according to the inventionguide surfaces are located in the form of steps at different levelsabove the bottom of the chamber and the means for supplying primarycombustion air open into the primary combustion chamber in zones betweenthe guide surfaces or between the lowermost guide surface and the bottomof said chamber.

The introduction of primary combustion air in the zones between theguide surfaces mounted in the form of steps has the effect of coolingthe underside of the guide elements so as to avoid an excessive heatingof said elements.

The guide elements preferably consist of small plate elements which aremounted adjacent to one another inrows extending transversely of theincinerator. In another preferred embodiment of the incineratoraccording to the invention the guide elements are supported by hollowmetal pipes which serve as means for introducing primary combustion air.By supplying primary combustion air through said supporting pipes, thelatter are cooled so that a deflection thereof can be avoided.Furthermore, the use of such supporting pipes permits in a simple mannera selective introduction of combustion air at diflerent levels withinthe combustion zone. In a still further embodiment of the incineratoraccording to the invention the hollow metal pipes are provided withdischarge openings located so as to direct streams of gas against theupper surface of the underlying guide surface. Thus, the air flowing outfrom said openings causes said guide elements to be cooled. Theincinerator according to the invention is preferably constructed in sucha manner that a relatively large amount of combustion air can besupplied at the lowermost guide surfaces in order to ensure that plasticmaterial which without burning completely out has reached the bottom ofthe incinerator is caused to burn at this place.

In a further preferred embodiment of the incinerator according to theinvention the lowermost portion of the walls of the primary combustionchamber form said guide surfaces and the means for introducing primaryair consist of downwardly inclined ducts provided in the walls of theprimary combustion chamber.

The secondary combustion chamber may be separated into a number ofadjacent and interconnected combustion chambers lined with refractoryceramic materials or other materials capable of resisting hightemperatures.

The secondary combustion chamber or chambers are preferably constructedin such a manner that the first part thereof is in connection with theprimary combustion chamber through an intermediate chamber or passage inwhich the direction of the flow of gases is turned I80The shape of thesecondary combustion chamber or chambers is not critical but in order toreduce the production costs it is preferred to use a secondarycombustion chamber having a rectangular cross section. The secondarycombustion chamber preferably comprises restrictions at the inlet andoutlet ends for the flue gases. The means for initiating a secondarycombustion preferably consist of one or more oil burners, gas burners orspark igniters provided in the wall of the secondary combustion chamber.There is preferably provided means for supplying air to the combustionin the secondary combustion chamber. The air supply means can be nozzleslocated at different locations relative to the flow direction of theflue gases. Nozzles located at opposite sides of the flow channel arepreferably offset relative to one another.

In order to reduce the loss of draught which is caused by the flow offlue gases through the secondary combustion chamber, it is preferred tomount the air supply nozzles in such a manner so as to direct thestreams of air generated therein in the direction of movement of theflue gases. Due to the fact that the secondary combustion is effected ina zone which is thermally separated from the primary combustion zone, itis possi ble by adjusting the amount of air supplied through the airnozzles to effect a combustion which at any time is adjusted to theamount of gases and soot particles which is fed to the secondarycombustion chamber. If air was introduced in an amount so as to ensure acomplete combustion at any given time too much air would be introducedover long periods and consequently, the combustion chamber would becooled. Thus, an incomplete combustion would take place and this wouldlead to high contents of soot in the gases leaving the secondarycombustion chamber.

Instead of using air nozzles having separate feeding means it ispreferred to feed the air through a pipe which is closed at one end andwhich comprises a wall having a large number of perforations, which pipeis located centrally within the secondary combustion chamber. By using apipe comprising perforations which are of different sizes within thedifferent zones of the combustion chamber, the air may be introduced ina pre-determined pattern.

The openings connected to the air supply means can also be openings inthe walls of the secondary combustion chamber. These openings areconnected with a head box on the exterior side of said walls, and air issupplied to said head box from the atmosphere by means of a pumpconnected to said head box.

A preferred embodiment of the incinerator according to the inventioncomprises means for automatically controlling the ratio of air suppliedto the primary combustion chamber to air supplied to the secondarycombustion chamber. These means are controlled by the heat generationand consequently the temperature within the secondary combustionchamber. This may be effected by providing within the secondarycombustion chamber a thermo couple which is connected to a regulator onwhich the maximum temperature permitted within the secondary combustionchamber can be set. The regulator is connected to a regulating damperwhich controls the supply of air to the primary combustion chamber andthe secondary combustion chamber, respectively. By means of aservo-control system it is possible in the manner described above toeffect a continuous regulation of the supply of air to the primarycombustion chamber and the secondary combustion chamber, respectively.In the incinerator according to the invention the combustion air mayalso be supplied to the combustion chambers in an amount which dependson the temperature within the primary combustion chamber.

Finally, the incinerator according to the invention may be constructedin such a manner that the supply of air is controlled by a soot detectormounted close to the secondary combustion chamber at the downstream sidethereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a verticalsectional view of an embodiment of the incinerator according to theinvention,

FIG. 2 illustrates a vertical sectional view of a second embodiment ofthe incinerator according to the invention,

FIG. 3 illustrates a horizontal sectional view of the incinerator shownin FIG. 2 along the line IIIllI,

FIG. 4 illustrates a vertical sectional view of a third embodiment ofthe incinerator according to the invention,

FIG. 5 illustrates a vertical sectional view of the secondary combustionchamber in a further embodiment of the incinerator according to theinvention,

FIG. 6 illustrates a vertical sectional view of the secondary combustionchamber in a still further embodiment of the incinerator according tothe invention,

FIG. 7 illustrates a vertical sectional view of the primary combustionchamber in a further embodiment of the incinerator according to theinvention, and

FIG. 8 illustrates a vertical sectional view of the primary combustionchamber shown in FIG. 7 along the line VII-VII.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings 1 is a primarycombustion chamber containing inclined guide elements 2 of a refractoryceramic material. These guide elements 2 are supported by hollow metalpipes 3 provided with holes and connected to means for supplying primarycombustion air to the combustion chamber. The primary combustion chamberis connected to a secondary combustion chamber 6 through a duct 4 and aflow-tuming chamber 5. In an opening in the wall of the secondarycombustion chamber 6 there is provided an oil burner 7 and a largenumber of air supply nozzles 8.

The secondary combustions chamber shown in FIGS. 2 and 3 also comprisesa large number of air supply nozzles 8. These air supply nozzles 8 areconnected through ducts 9 with air supply compartments 10 mounted atopposite sides of the secondary combustion chamber. Air is supplied tosaid compartments 10 through pipes 11. Temperature sensors 22 and 24 arerespectively mounted in secondary combustion chamber 6 and primarycombustion chamber 1 and provide signals to air delivery controller 23for the purpose of varying the supply of air to combustion chamber 1 inaccordance with either the temperature of the first or secondarycombustion chamber. As mentioned previously, another means ofcontrolling the supply of air to combustion chamber 1 is to sense theamount of soot emanating from the second combustion chamber, and forsuch a control, the temperature sensor 22 may be replaced by a sootsensor which is mounted close to the secondary combustion chamber at thedownstream side thereof. In the incinerator illustrated in FIG. 4central guide elements 12 supported by air supply pipes are providedwithin the primary combustion chamber. These central guide elements 12permit a satisfactory supply of air to that portion of the plasticmaterial which during the incineration is located at the center of theprimary combustion chamber.

In the secondary combustion chamber shown in FIG. 5 there is provided acentral air supply pipe 13 which is closed at its lowermost end andwhich is provided with horizontal rows of holes 14. The distance betweenthe rows is less in the restricted area at the outlet of the secondarycombustion chamber 6 than at the center thereof. This pipe 13 permitsthe supply of different amounts of air to different portions of thesecondary combustion chamber.

The secondary combustion chamber shown in FIG. 6 consists of twocylindrical concentrically mounted pipes 15 and 16, of which theinnermost one 16 is made from stainless steel. The space between the twopipes forms an air supply compartment 17 to which air is suppliedthrough a pipe 18. The innermost pipe 16 is provided with horizontalrows of holes 14 through which the air supplied is introduced into thesecondary combustion chamber. In the incinerators disclosed an oilburner (not shown) is mounted in the side wall of the primary combustionchamber. This oil burner serves to initiate the combustion within theprimary combustion chamber.

In the incinerator illustrated in FIGS. 7 and 8 the side walls of theprimary combustion chamber 1 form inclined guide surfaces 19 of arefractory ceramic material. Downwardly directed ducts 20 for theintroduction of primary combustion air are provided in said side walls.

The incinerator shown in FIGS. 7 and 8 is preferably connected to asecondary combustion chamber of the type shown in FIG. 6. a

I claim:

1. An incinerator for the combustion of waste products and particularlyplastic materials comprising a primary combustion chamber, means forsupplying combustion air to said primary combustion chamber, a secondarycombustion chamber thermally isolated from the primary combustionchamber, means for initiating a secondary combustion and means forsupplying combustion air within said secondary combustion chamber, theprimary combustion chamber comprises inclined continuous guide surfacesconsisting of guide elements made from a refractory ceramic material,said guide surfaces are mounted at difi'erent levels within said primarycombustion chamber, and said means for supplying primary combustion airto said primary combustion chamber open into said chamber between saidinclined guide surfaces.

2. An incinerator according to claim 1, wherein said guide surfaces arein the form of steps at difierent levels above the bottom of the primarycombustion chamber, and said means for supplying primary combustion airopen into the combustion chamber in zones between the guide surfaces andbetween the lowermost guide surface and the bottom of the primarycombustion chamber.

3. An incinerator according to claim 2, further comprising hollow pipesfor supporting said guide elements and for introducing primarycombustion air into the primary com bustion chamber.

4. An incinerator according to claim 3, wherein said hollow pipesinclude discharge openings located so as to direct streams of gasgenerated therein against the upper surface of the underlying guideelements.

5. An incinerator according to claim 1, wherein the lowermost portion ofthe walls of the primary combustion chamber form said guide surfaces andthat the means for supplying primary combustion air to the primarycombustion chamber consist of downwardly inclined ducts provided in thewalls of said primary combustion chamber.

6. An incinerator according to claim 1, further comprising means forcontrolling the amount of air supplied to the prima ry combustionchamber dependent on the generation ofheat within the secondarycombustion chamber.

7. An incinerator according to claim 1, further comprising means forcontrolling the supply of air to the primary combustion chamberdependent on the generation of heat in the primary combustion chamber.

8. An incinerator according to claim 1, further comprising means forcontrolling the supply of air to the primary combustion chamberdependent on the contents of soot in the flue gases leaving thesecondary combustion chamber.

1. An incinerator for the combustion of waste products and particularlyplastic materials comprising a primary combustion chamber, means forsupplying combustion air to said primary combustion chamber, a secondarycombustion chamber thermally isolated from the primary combustionchamber, means for initiating a secondary combustion and means forsupplying combustion air within said secondary combustion chamber, theprimary combustion chamber comprises inclined continuous guide surfacesconsisting of guide elements made from a refractory ceramic material,said guide surfaces are mounted at different levels within said primarycombustion chamber, and said means for supplying primary combustion airto said primary combustion chamber open into said chamber between saidinclined guide surfaces.
 2. An incinerator according to claim 1, whereinsaid guide surfaces are in the form of steps at different levels abovethe bottom of the primary combustion chamber, and said means forsupplying primary combustion air open into the combustion chamber inzones between the guide surfaces and between the lowermost guide surfaceand the bottom of the primary combustion chamber.
 3. An incineratoraccording to claim 2, further comprising hollow pipes for supportingsaid guide elements and for introducing primary combustion air into theprimary combustion chamber.
 4. An incinerator according to claim 3,wherein said hollow pipes include discharge openings located so as todirect streams of gas generated therein against the upper surface of theunderlying guide elements.
 5. An incinerator according to claim 1,wherein the lowermost portion of the walls of the primary combustionchamber form said guide surfaces and that the means for supplyingprimary combustion air to the primary combustion chamber consist ofdownwardly inclined ducts provided in the walls of said primarycombustion chamber.
 6. An incinerator according to claim 1, furthercomprising means for controlling the amount of air supplied to theprimary combustion chamber dependent on the generation of heat withinthe secondary combustion chamber.
 7. An incinerator according to claim1, further comprising means for controlling the supply of air to theprimary combustion chamber dependent on the generation of heat in theprimary combustion chamber.
 8. An incinerator according to claim 1,further comprising means for controlling the supply of air to theprimary combustion chamber dependent on the contents of soot in the fluegases leaving the secondary combustion chamber.